Yes, I agree, it is a high risked deal, But you may try in a small amounts! You never know what will be a new trend tomorrow!From my own experience: Instagram Influencers are flaky and happy to screw you over, no matter how big they are. They are not at risk of losing their followers if they scam you in any way.
From the experience I have heard from others: Always negotiate a % of the sales or give them an affiliate code to track sales. You can offer a small amount guaranteed up front, but keep it small until they have proven themselves.